This project involves the development of "expert systems" in the medical environment. Expert systems represent feasible applications of artificial intelligence techniques. They are knowledge-based, in that they contain knowledge contributed by experts, and organized, by "knowledge engineers." Generally, they function best in specific, narrowly defined, yet still complex, problem areas. A very important characteristic of these systems is that decisions and recommendations are explained and justified to the user. An initial objective for the project is to develop, in collaboration with the Critical Care Medicine Department of the Clinical Center, a Therapy Advisor Expert System for use in an Intensive Care Unit. The drug administration protocol includes the capability for long-term dose maintenance and eventual dose tapering. Personal computer based technology (IBM PC-XT or PC-AT) has been utilized in conjunction with commercial expert system shells and an original generated BASIC approach.